Adding until-error and updating README.md

Author: KrustyHack

README.md

@@ -392,6 +392,24 @@ Alternatives:
 * `until-success ping -c 1 1.2.3.4; ssh user@1.2.3.4`
 
 
+
+until-error
+-------------
+
+Repeat the specific command until it fails - run at least once
+always.
+
+Example:
+
+         ./until-error ssh example.com -l root -i ~/.ssh/example.com.key
+
+Trivial (ba)sh alternatives:
+
+* while true ; do $cmd; done
+* watch -n 2 $cmd
+
+
+
 when-down
 -------
 
@@ -403,6 +421,10 @@ Example:
      Waiting for 1.2.3.4 to get down...
      down
 
+Alternatives:
+
+* `until-error ping -c 1 -W 1 1.2.3.4; echo "down"`
+
 
 
 which-shell

until-error

@@ -0,0 +1,17 @@
+#!/bin/sh
+#
+# About
+# -----
+# Repeat the command until it fails
+#
+
+"$@"
+
+#
+#  If the status code was zero then repeat.
+#
+while [ $? -eq 0 ]; do
+    "$@"
+done
+
+